Hmm...seems to be screwed up firmware. What was the original reason for You to upgrade the firmware? IIRC there was some vulnerability in the Original firmware but that could be exploited only if your router's Configuration page was exposed to the Internet.
I had once tried upgrading the firmware but even that is not so simple in 502T's case, it messed up the router and it had to be replaced....thankfully the MTNL guys did so within a day. Now that's one more point in MTNL Triband's favour , atleast their CC has improved a lot.
Regards, Antriksh